LifePo4 Charge Performance

BFL13 wrote:
Looks like LFP owners should have a 10 amp ordinary car battery charger along as part of their kits. Often recommended anyway in case of converter failure so you can keep on camping.

Procedure for recharging LFPs that are below freezing:
1. heat them up to above freezing
2. charge at 10 amps till they are above 41F (charging will continue to heat them up) Leave heater on if gen can do both.
3. swap over to your high amp charger once they are above 41F

Beware of your solar amps, might have to switch off solar.

If the LFPs are outside on the tongue and never get above 41F, get more gas for your generator to keep charging at 10 amps for the month of Sundays that will take.

Have a way to measure your LFP battery cell temperature (as mentioned by itinerant1)

no need for that, we use them at work on the big trucks, they take full charge at 0 and they arn't replaced any more than any other battery just get a proper Li compatable charger and go camping. bettery yet get a tempature compensated Li charger that throws a temp sensor on the battery pack. I dont know why your hell bent on trying to say you have to go lower current till 41F as no cell speck I have looked up has sed that, but if you go LiFePo4 and want to carry another charge then by all means.

but lets just check this out, here is the specs for some higher quality 271ah cells

Model RJ-LFP71173200-271
Casing material for single cell Aluminum shell
Nominal Voltage 3.2V
Capacity 271Ah
Core size D71*W173*H200MM
Cell Weight 5.4KG
Charging Current Standard Charging:0.2C
Max Charging:1C

Max Discharging Rate Continuous Discharging:2C
Cut-off Voltage Charging:3.65V
Discharging:2.5V
Internal Resistance 0.5m? (At 0.2C rate, 2.0V cut-off)
Working Temperature Charging: -10°C~55°C
Discharging: -20°C~70°C
Storage Temperature 1month: -10–45°C
3month: 0–30°C
6month: 20±5°C
Life Cycle >6000 times (100% DOD)

so if I build a two battery set up for the rv then I would have 542AH @ 12V so yes you can charge them at 1C wich would be a 542A charger, but lets not kid anyone who is going to do that? if you read the specs they recomend a 0.2C charge wich would be 108A , really who is going to do that even. so lets say that we use a 75 amp charger (one of the bigger rv setups. I have seen 90amp converters but not very often) thats a 0.14C charge rate which would mean your always charging a lower rate anyways so even if one banufacturer says to charge slower in that first 5 degrees , you always are.

if you also look at the specks it has charging from -10C - 55C

so alot of these "other requirments" may deal with different types of battery housing formats, or maybe they are just battery companys ways to increase the life so they wont have to replace stuff under warenty if some one uses it outside of there secs or maybe there just using lower quality cells.

Steve